JPH1061412A - Controller for combined cycle power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize steam pressure supplied to a steam turbine regardless of delay of starting action for closing a turbine bypass valve when a steam governing valve is started to be opened, by controlling the steam governing valve according to deviation between the actual steam pressure and set steam pressure of steam while the turbine bypass valve is closed. SOLUTION: When a gas turbine is started, steam pressure generated in an exhaust heat recovering boiler is detected by a pressure sensor 41, and an actual steam pressure signal (b) is compared with a set steam pressure signal (a) in an adder-subtracter 39, and when the signal (b) is higher, a turbine bypass valve 42 is opened. Also, an actual lift signal (g) by a valve lift detector 43 is compared with a regulated signal (h) in a comparator 45, and when the signal (g) is higher, a switch 49 is switched on. Also, in the case that deviation between the signals (a) and (b) is lower than a set value, a switch 50 is switched on by the output of a comparator 40. Hereby, an opening change rate signal (f) from a setting apparatus 48 is applied as a loading signal (c) to a change-over apparatus 48, and the loading signal (c) is applied as a valve opening signal (e) to a steam governing valve 53.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a combined cycle power plant,
The present invention relates to a control device for a combined cycle power plant that suppresses steam pressure fluctuations generated when steam supplied from an exhaust heat recovery boiler to a turbine bypass system is transferred to a steam turbine.

[0002]

2. Description of the Related Art In general, a combined cycle power plant is obtained by combining a gas turbine plant and a steam turbine plant to greatly improve the thermal efficiency of a conventional thermal power plant. .

[0003] The combined cycle power plant 1 comprises:
A gas turbine plant 3 and a steam turbine plant 4 having a common rotating shaft 2 and a separately disposed exhaust heat recovery boiler 5 are provided.

The gas turbine plant 3 includes an air compressor 6, a combustor 7, a fuel valve 8, and a gas turbine 9. The air sucked by the air compressor 6 is pressurized, and the high-pressure air is supplied to the fuel from the fuel valve 8. The combustion gas is generated in the combustor 7, the combustion gas is guided to the gas turbine 9 to perform expansion work, and the steam turbine 10 and the generator 11 are driven by the rotational power obtained by the expansion work. The expanded exhaust gas (exhaust heat) is supplied to the exhaust heat recovery boiler 5 as a heat source for generating steam.

The exhaust heat recovery boiler 5 generates steam from the exhaust gas supplied from the gas turbine 9 and supplies the steam to a steam turbine plant.

The steam turbine plant 4 includes a pressure sensor 12, a steam control valve 13, a steam turbine 10, a condenser 14, and a turbine bypass system 15. The steam turbine 10 uses steam supplied from the exhaust heat recovery boiler 5. While the generator 11 is driven together with the rotational power obtained by the expansion work and the rotational power of the gas turbine 9.
The exhaust steam after the expansion work is guided to the condenser 14, where it is condensed to be condensed, and the condensed water is returned to the exhaust heat recovery boiler 5 as feed water.

In the steam turbine plant 4, during startup operation, the steam generated from the exhaust heat recovery boiler 5 has a rated pressure,
Since the temperature has not been reached, the turbine bypass valve 16 of the turbine bypass system 15 is opened, and the steam is supplied to the condenser 14 until the rated pressure and temperature are reached.

Further, the fuel valve 8, the steam control valve 13, and the turbine bypass valve 16 are opened and closed by a control device 18. In particular, during startup operation, the pressure of steam supplied from the exhaust heat recovery boiler 5 to the turbine bypass system 15 is detected by the pressure sensor 12,
The detected steam pressure signal is input to the control device 18 where a valve opening / closing operation is performed. The valve opening / closing signal is supplied to the turbine bypass valve 16 to open and close the valve. The valve lift signal is detected, and the valve lift signal is fed back to the control device 18, and the valve lift of the turbine bypass valve 16 is corrected by the feedback signal to control the flow rate.

As described above, while the control device 18 controls the valve lift of the turbine bypass valve 16,
When the pressure sensor 12 detects that the pressure and temperature of the steam generated from the exhaust heat recovery boiler 5 reach the rating, the turbine bypass valve 16 is closed, the fuel valve 8 and the steam control valve 13 are closed.
Is fully opened.

On the other hand, a specific circuit of the control device 18 is shown in FIG.
As shown in the figure, the turbine bypass valve setting device 19 and the turbine bypass valve controller 20 are provided, and the actual steam pressure signal b detected by the pressure sensor 12 and the setting valve opening signal a of the turbine bypass setting device 19 are transmitted to the turbine. Match by the bypass valve controller 20 and determine the deviation by P
ID calculation is performed, and the turbine bypass valve 16 is opened and closed by the PID calculation signal.

Further, the control device 18 controls the exhaust heat recovery boiler 5
When the steam pressure reaches a predetermined value, the valve switching drive unit 21 switches from opening and closing the turbine bypass valve 16 to opening and closing the steam control valve 13, and loading control for opening and closing the steam control valve 13 during startup operation. Unit 22, a pressure control unit 23 that opens and closes the steam control valve 13 during rated operation, and a steam control valve by switching to one of the loading signal c of the loading control unit 22 and the pressure signal d of the pressure control unit 23. 13 is provided with a switch 28 for giving a valve opening / closing signal e.

Here, the loading control means that the turbine bypass system 1 is operated until the steam generated from the exhaust heat recovery boiler 5 reaches a pressure that can be supplied to the steam turbine 10.
5 is a control that gradually shifts from the opening and closing of the turbine bypass valve to the opening and closing of the steam control valve 13 while maintaining the pressure of the steam flowing in the fuel cell 5 constant.

The valve switching drive section 21 includes a first comparator 2
4. A turbine bypass valve provided with a second comparator 25, a memory 26, and an AND gate 27. The first comparator 24 sets a real lift signal g of the turbine bypass valve 16 detected by the valve lift detector 17 in advance. When the actual lift signal g is lower, the first comparator 24 is energized and input to the AND gate 27. Further, the valve switching drive unit 21 compares the actual lift signal g of the turbine bypass valve 16 detected by the valve lift detector 17 with a preset turbine bypass valve regulation signal h by the second comparator 25, and the actual lift signal g Is higher, the second comparator 45 is energized and stored in the memory 26.

The memory 26 outputs the stored signal to the AND gate 2
7 and the loading control unit 22.

The loading control unit 22 includes a setting unit 29,
A switch 30 and an integrator 31 are provided. When the switch 30 is turned on by the output of the valve switching drive unit 21, a valve opening / closing change rate signal f set in advance by a setter 29 is input to the integrator 31 for calculation and loading. The switch 28 is energized as a signal c.

The pressure control unit 23 is not directly related to the present invention, and the detailed description of the circuit is omitted. However, when the steam is pressure-controlled during rated operation, the switch 28 is energized as a pressure signal d. It has become.

Next, the operation of the control device of the combined cycle power plant during the start-up operation will be described.

When the gas turbine 9 is started, fuel is supplied from the fuel valve 8 to the combustor 7, and the fuel is ignited to generate combustion gas, the combustor 7 transfers the combustion gas to the gas turbine 9. The exhaust gas after the expansion work is guided to the exhaust heat recovery boiler 5 as the steam generation heat source.

The exhaust heat recovery boiler 5 gradually generates steam, and the steam pressure gradually increases as the amount of generated steam increases.

The pressure sensor 12 constantly detects the pressure of the steam generated from the exhaust heat recovery boiler 5 and inputs the actual steam pressure signal b to the controller 20 for the turbine bypass valve. The turbine bypass valve controller 20 compares the actual steam pressure signal b with the set pressure signal a from the turbine bypass valve setter 19, and outputs the actual steam pressure signal b
Is higher, the deviation is used as the valve opening / closing signal as PID
The calculation is performed, and the turbine bypass valve 16 is opened. Further, when the steam generated from the exhaust heat recovery boiler 5 increases,
Since the steam pressure also increases, in order to keep the steam pressure substantially constant, the controller 20 for the turbine bypass valve
The turbine bypass valve 16 is opened.

As described above, while the turbine bypass valve 16 is being opened, the valve lift detector 17 detects the valve lift of the turbine bypass valve 16 and outputs the detected actual lift signal g to the first comparator 24 and the first comparator 24. 2 is input to each of the comparators 25.

The first comparator 24 matches the actual lift signal g with a preset slightly opened signal for turbine bypass valve i. In this case, since the actual lift signal g is higher, the current is cut off. .

On the other hand, the second comparator 25 outputs the actual lift signal,
Since the actual valve lift signal g is higher than the preset turbine bypass valve regulation signal h, the current is directly supplied and stored in the memory 26, and the switch 30 of the loading control unit 23 is turned on.

The loading control unit 22 includes a switch 30
Is turned on, the valve opening / closing change rate signal f of the setter 29 is input to the integrator 31 for calculation, and is input to the switch 28 as the loading signal c. In this case, the switch 28
Is turned ON to the contact a side from the beginning, the steam control valve 13 is opened using the loading signal c as the valve opening / closing signal e.

Thus, as the steam control valve 13 is opened and the flow rate of the steam flowing from the exhaust heat recovery boiler 5 to the steam turbine 10 increases, the steam pressure decreases. When the steam pressure decreases, the actual steam pressure signal b input to the turbine bypass valve controller 20 becomes lower than the set pressure signal a of the turbine bypass valve setter 19, so that the turbine bypass valve controller 20 PID the deviation
Calculation is performed, and the calculation signal is supplied to the turbine bypass valve 16 to start valve closing. At this time, even if the actual lift signal g detected by the valve lift detector 17 is lower than the turbine bypass valve prescribed signal h by the second comparator 25, the memory 26
Since the first actual lift signal g stored in
The switch 30 of the loading control unit 22 is maintained in the ON state. Therefore, the steam control valve 13 continues to open.

While the steam control valve 13 keeps on opening, the turbine bypass valve 16 keeps closing. During this time, the actual lift signal g of the valve lift detector 17 that has detected the valve lift of the turbine bypass valve 16 is lower than the turbine bypass valve slightly open signal i of the first comparator 24, so that the actual lift signal g is The current is supplied to the AND gate 27 together with the actual lift signal g for energizing the first comparator 24 and energizing the second comparator 25. The AND gate 27 has two actual lift signals g.
Is completed, the loading control is terminated by moving the switch of the switch 28 from the contact a to the contact b.

When the loading control is completed and the turbine bypass valve 16 is fully closed, the pressure control unit 23 inputs the pressure control signal d to the switch 28 and gives it to the steam control valve 13 as a valve opening / closing command signal e. After that, the steam control valve 13
To pressure control. At the time of shifting to the pressure control of the steam control valve 13, the pressure control unit 23 tracks the loading signal c of the loading control unit 22, but the control unit of the steam control valve 13 is directly related to the present invention. The description is omitted because it is not relevant.

As described above, in the control device of the conventional combined cycle power plant, during start-up operation, the control command of the loading control unit shifts the valve opening / closing control of the turbine bypass valve to the valve opening / closing control of the steam control valve, while controlling the turbine. At the time of valve opening / closing control of the bypass valve, the actual steam pressure signal is made to follow the set pressure signal, and the exhaust heat recovery boiler 5
By maintaining the pressure of the steam supplied to the turbine bypass system 15 at a substantially constant level, the steam generated from the exhaust heat recovery boiler 5 is stabilized.

[0029]

By the way, in the conventional control device of the combined cycle power plant, as shown in FIG. 6, the valve of the steam control valve 13 starts to open and the turbine bypass valve 16 starts to close at the same time. The steam control valve 13
At the same time as the end of the full opening of the valve, the valve of the turbine bypass valve 16 is fully closed, and the loading control is performed so that the actual steam pressure of the steam generated from the exhaust heat recovery boiler 5 follows a predetermined set pressure. However, in practice, a phenomenon has occurred in which the actual steam pressure is greatly reduced (pressure deviation), and the set pressure cannot be followed.

The cause of the decrease in the actual steam pressure with respect to the set pressure is that the turbine bypass valve 16 is a valve opening / closing control by PID calculation, and therefore requires a little time for the calculation. It is considered that this occurs because the closing start operation is delayed. That is, when the steam control valve 13 starts the valve opening operation, the steam pressure decreases, but at this point, it is considered that the turbine bypass valve 16 has not started the valve closing operation.

As described above, in the conventional loading control,
The operation of opening the valve of the turbine bypass valve 16 was delayed with respect to the start of opening the steam control valve 13.

If the operation of starting the valve closing of the turbine bypass valve 16 is delayed, the loading control is started while the steam pressure is reduced, and the steam pressure is further reduced. There has been a problem that the flow rate of steam generated from the steam drum becomes unstable, the water level of the steam drum fluctuates, and the exhaust heat recovery boiler 5 must be operated in an unstable manner.

The present invention has been made in view of such a technical background. Even if the operation of starting the closing of the turbine bypass valve is delayed with respect to the operation of starting the opening of the steam control valve,
An object of the present invention is to provide a control device for a combined cycle power plant that stabilizes the pressure of steam supplied from an exhaust heat recovery boiler to a steam turbine.

[0034]

In order to achieve the above object, a control apparatus for a combined cycle power plant according to the present invention has a gas turbine plant, a steam turbine plant, and a waste heat recovery system. Combining the boilers, during the start-up operation of the exhaust heat recovery boiler, while flowing the steam generated from the exhaust heat recovery boiler to the turbine bypass system,
When the steam pressure exceeds a certain value, in the control device of the combined cycle power plant including a control unit that provides a valve closing signal to the turbine bypass valve and provides a valve closing signal to the steam control valve, the control unit includes: A loading control unit including a first switch and a second switch for controlling the opening and closing of the steam control valve, and a first switch of the loading control unit when the turbine bypass valve is closed.
N: a valve switching drive unit, a deviation calculation unit that calculates a deviation by comparing an actual steam pressure of steam generated from the exhaust heat recovery boiler with a set steam pressure while the turbine bypass valve is closed, and calculating the deviation. When the output of the unit is lower than the first deviation set pressure value, the second switch of the loading control unit is turned ON. When the output of the deviation calculation unit is higher than the second deviation set pressure value, the loading control unit A turbine bypass control unit incorporating a calculation unit for turning off the second switch, and a steam control valve which is opened when both the first switch and the second switch of the loading control unit are turned on. The operation signal from the operation unit is cut off, and the second switch is set to O
A switching device for holding the valve opening of the steam control valve when the FF is performed.

In order to achieve the above object, the control apparatus for a combined cycle power plant according to the present invention has a deviation calculating section incorporated in the turbine bypass control section. The calculation unit is an adder / subtractor.

According to a third aspect of the present invention, there is provided a control apparatus for a combined cycle power plant, wherein an adder / subtractor includes a turbine bypass valve which outputs an actual steam pressure signal from a pressure sensor to a turbine bypass valve. The deviation is calculated by matching predetermined pressure signals from a closed setting device.

In the control apparatus for a combined cycle power plant according to the present invention, in order to achieve the above object, an arithmetic unit is incorporated in the turbine bypass control unit. Is a comparator having a set value different from the first deviation set pressure value and the second deviation set pressure value.

In order to achieve the above object, the control device for a combined cycle power plant according to the present invention is configured such that the turbine bypass control unit includes an actual steam of steam generated from the exhaust heat recovery boiler. A differentiator for calculating the rate of change of pressure, and when the operation signal of the differentiator is lower than the first deviation set pressure value, the second switch of the loading control unit is turned on, and the operation signal of the differentiator is set to the second deviation setting And a comparator that cuts off when the pressure is higher than the pressure value and turns off the second switch of the loading control unit.

[0039]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device for a combined cycle power plant according to the present invention will be described below with reference to the drawings.

FIG. 1 is a control block diagram schematically showing a control device of a combined cycle power plant according to the present invention.

The control device 32 according to this embodiment includes a turbine bypass control unit 33, a valve switching drive unit 34, a loading control unit 35, and a pressure control unit 36.

The turbine bypass controller 33 includes a turbine bypass valve setting device 37, a turbine bypass valve controller 38, an adder / subtractor 39, and a comparator 40 having different deviation set pressure values. The actual steam pressure signal b is compared with the set steam pressure signal a of the turbine bypass valve setter 37 by the adder / subtractor 39, and the deviation j is compared with the first deviation set pressure value (1/2) by the comparator 40.
When it is lower than ε), the comparator 40 is energized and the second switch 50 of the loading control unit 35 is turned on. When the deviation j is higher than the second deviation set pressure value (ε) in the comparator 40, the power supply to the comparator 40 is cut off and the second switch 50 of the loading control unit 35 is turned off.
It is designed to be flipped.

The actual steam pressure signal b is compared with the set steam pressure signal a of the turbine bypass valve setting device 37 by the turbine bypass valve controller 38, and the deviation is represented by P.
ID calculation is performed, and the calculation signal is supplied to the turbine bypass valve 42 as a valve opening / closing signal to open and close the turbine bypass valve 42.

The valve switching drive unit 34 includes a first comparator 44, a second comparator 45, a memory 46, and an AND gate 4.
7, the actual lift signal g of the turbine bypass valve 42 detected by the valve lift detector 43 is input to each of the first comparator 44 and the second comparator 45, and the first comparator 44
The actual lift signal g is matched with a preset turbine bypass valve opening fine opening signal i. When the actual lift signal g is higher, the energization of the first comparator 44 is cut off, and when the actual lift signal g is lower, The first comparator 44 is energized and input to the AND gate 47. Further, the valve switching drive unit 34 compares the actual lift signal g and the preset turbine bypass valve regulation signal h with the second comparator 4.
When the actual lift signal g is higher, the second comparator 45 is energized and stored in the memory 46. Further, the memory 46 outputs the storage signal k to A
It is input to each of the ND gate 47 and the loading control unit 35.

On the other hand, the loading control unit 35 includes a setter 48, a first switch 49, a second switch 50, an integrator 5
When the first switch 49 and the second switch 50 are turned on by the output of the valve switching drive unit 34 and the output of the turbine bypass control unit 33, respectively, the setting unit 4
The valve opening / closing change rate signal f set in advance by the
, And a current is supplied to the contact a of the switch 48 as a loading signal c.

The pressure control unit 36 controls the pressure of the steam supplied from the exhaust heat recovery boiler to the steam turbine.
A pressure signal d is output, and the pressure signal d is
Is given to the steam control valve 49 as the valve opening command signal e through the above. However, since the pressure control here is not directly related to the present invention, the description of the specific circuit is omitted.

Next, the operation will be described.

When the gas turbine is started, exhaust gas is supplied from the gas turbine to the exhaust heat recovery boiler,
Steam is generated from the exhaust heat recovery boiler, and the pressure gradually increases. The steam pressure is detected by the pressure sensor 41, and one of the actual steam pressure signals b is input to the adder / subtractor 39 of the turbine bypass control unit 33 and the other to the controller 38 for the turbine bypass valve.

Controller 38 for turbine bypass valve
Matches the actual steam pressure signal b with the set steam pressure signal a from the turbine bypass valve setter 37, and opens the turbine bypass valve 42 when the actual steam pressure signal b is higher.

During the opening of the turbine bypass valve 42, the valve lift detector 43 detects the valve lift of the turbine bypass valve 42 and outputs the actual lift signal g to the valve switching drive unit 34.
Are input to the first comparator 44 and the second comparator 45, respectively.

The first comparator 44 matches the actual lift signal g with the preset slightly-opened signal for turbine bypass valve i. At this time, the actual lift signal g is higher than the actual lift signal g. Cut the passage.

The second comparator 45 outputs the actual lift signal g
Is compared with the preset turbine bypass valve regulation signal h. However, since the actual lift signal g is higher, the second comparator 45 is energized and stored in the memory 46, and the output signal k is used as the loading control unit. The first switch 49 of 35 is turned on.

On the other hand, the adder / subtractor 39 of the turbine bypass control section 33 matches the actual steam pressure signal b detected by the pressure sensor 41 with the set steam pressure signal a from the turbine bypass valve setting device 37, and the deviation j thereof is determined. Comparator 40
Is lower than the first deviation set pressure value (1 / 2ε) of the loading control unit 35, the second switch 50 of the loading control unit 35 is turned off.
N.

In this way, each of the first switch 49 and the second switch 50 of the loading control unit 35 is turned on.
Then, the opening degree change rate signal f output from the setting unit 48
Are the first switch 49, the second switch 50, the integrator 51
, And the current is supplied to the contact a of the switch 48 as the loading signal c, and is supplied to the steam control valve 53 as the valve opening signal e after the power is supplied.

When the steam control valve 53 starts to open, the pressure of the steam supplied from the exhaust heat recovery boiler decreases, and the actual steam pressure signal b of the pressure sensor 41 is used as the value of the turbine bypass valve setter 37. Since it becomes lower than the set steam pressure signal, the valve of the turbine bypass valve 42 is started to be closed. However, a slight calculation delay occurs in the PID calculation of the turbine bypass valve controller 38. Valve closing has not been started. For this reason,
The actual steam pressure greatly falls from the set steam pressure as shown by the solid line in FIG.

When the actual steam pressure drops greatly from the set steam pressure, the deviation j of the adder / subtractor 39 of the turbine bypass controller 33 exceeds the second set pressure value (ε) of the comparator 40, Is cut off, and the second switch 50 of the loading control unit 35 is turned off.

Since the second switch 50 is turned off, the loading control unit 35 temporarily cuts off the energization of the integrator 51 with the valve opening / closing change rate signal f of the setting unit 48. Therefore, the steam control valve 53 temporarily holds the valve opening as shown in FIG.

While the steam control valve 53 holds its valve opening, the actual steam pressure of the pressure sensor 41 is lower than the steam pressure set by the turbine bypass valve setter 37. The controller 38 continues to close the turbine bypass valve 42.

As described above, when the controller 38 for the turbine bypass valve continues to close the turbine bypass valve 42, the pressure of the steam supplied from the exhaust heat recovery boiler gradually starts increasing, and the deviation of the adder / subtractor 39 is increased. j also decreases, and when the deviation j becomes smaller due to the first deviation set pressure (1 / 2ε) of the comparator 40, the comparator 40 is energized, and the second switch 50 of the loading control unit 35 is turned on again. The valve opening of the steam control valve 53 is increased.

During the opening of the steam control valve 53, the pressure of the steam supplied from the exhaust heat recovery boiler decreases, and the deviation j of the adder / subtractor 39 becomes the second deviation set pressure (ε) of the comparator 40.
Then, as described above, the valve opening of the steam control valve 53 is temporarily held and the recovery of the steam pressure is waited.

While the steam control valve 53 temporarily holds the valve opening and recovers the steam pressure, the turbine bypass valve 42 continues to be closed. Turbine bypass valve 4
When the valve 2 approaches full valve closing, the valve lift detector 43 detects the actual valve lift signal g which is lower than the turbine bypass valve slightly open signal i of the comparator 44 of the valve switching drive unit 34. The lift signal g is input to the AND gate 47 via the comparator 44, and the switch 53 is shifted from the cut point a to the cut point b on condition that the output signal k of the memory 46 is completed, and the loading control is terminated. , Steam control valve 53
Pressure control is started.

As described above, in this embodiment, the actual steam pressure signal of the pressure sensor 41 and the setting device 3 for the turbine bypass valve are used.
7 is calculated by the adder / subtractor 39. When the deviation j is lower than the first deviation set pressure (1 / 2ε) of the comparator 40, the loading control unit 35
Is turned on to open the steam control valve 53, and when the deviation j is larger than the second deviation set pressure (ε) of the comparator 40, the second switch 50 of the loading control unit 35 is turned on. Since the valve is turned off and the valve opening of the steam control valve 53 is temporarily held, the pressure of steam supplied from the exhaust heat recovery boiler can be maintained substantially constant.

Therefore, in the present embodiment, the flow rate of steam generated from the steam drum of the exhaust heat recovery boiler is stabilized and the water level of the steam drum is prevented from fluctuating. Can be done.

FIG. 2 is a control block diagram schematically showing a first embodiment of a control device for a combined cycle power plant according to the present invention. The same components as those in the first embodiment are denoted by the same reference numerals, and different components will be described.

In this embodiment, the turbine bypass control unit 33
Is combined with a differentiator 54 and a comparator 55, and the pressure sensor 4
1, the change rate signal is calculated by the differentiator 54. When the absolute value of the calculation signal 1 is lower than the first deviation set pressure value (−ε) by the comparator 55, the comparison is performed. When the absolute value of the operation signal 1 is higher than the second deviation set pressure value (+ ε) in the comparator 55, the power of the comparator 55 is turned on. Is cut off, and the second switch 50 of the loading control unit 35 is turned off.

As described above, in this embodiment, the actual steam pressure signal b is calculated by the differentiator 54 into the change rate signal, and the absolute value of the calculation signal 1 is used as the first deviation set pressure value ( −ε), the second of the loading control unit 35
Turn on the switch 50, open the steam control valve 49,
When the steam pressure drops due to the opening of the steam control valve 49,
When the actual steam pressure signal b also drops and the absolute value of the operation signal 1 in the differentiator 54 becomes higher than the second deviation set pressure value (+ ε) of the comparator 55, the second switch 50 of the loading control unit 35 is turned off. Then, the valve opening of the steam control valve 49 is temporarily held, and according to the level of the actual steam pressure, similarly to the behavior of the valve opening of the steam control valve 49 shown in FIG.
Since the valve 9 is repeatedly opened and held, the pressure of the steam generated from the exhaust heat recovery boiler can be maintained substantially constant.

Therefore, also in the present embodiment, similarly to the first embodiment, the stable operation of the exhaust heat recovery boiler can be performed.

[0068]

As described above, the control device of the combined cycle power plant according to the present invention includes the turbine bypass control unit, the valve switching drive unit, the loading control unit, and the pressure control unit, and starts the exhaust heat recovery boiler. While the turbine bypass valve is closed during operation, the first switch of the loading control unit is turned on by the valve switching drive unit.
When the actual steam pressure generated from the exhaust heat recovery boiler is lower than the first deviation set pressure value of the comparator of the turbine bypass control, the second switch of the loading control unit is turned on to open the steam control valve. During the opening of the steam control valve, when the actual steam pressure of the steam generated from the exhaust heat recovery boiler becomes higher than the second deviation set pressure value of the setter of the turbine bypass valve, the second switch of the loading control unit is turned on. Is turned off and the steam control valve is controlled to maintain the valve opening of the steam control valve in the hold state, so that the steam pressure of the steam generated from the exhaust heat recovery boiler can be maintained substantially constant. it can.

Therefore, in the control device of the combined cycle power plant according to the present invention, the steam pressure of the steam generated from the exhaust heat recovery boiler can be maintained almost constant, so that the control from the loading control of the steam control valve to the pressure control is performed. Can be smoothly performed.

[Brief description of the drawings]

FIG. 1 is a control block diagram schematically showing a first embodiment of a control device for a combined cycle power plant according to the present invention.

FIG. 2 is a control block diagram schematically showing a first embodiment of a control device for a combined cycle power plant according to the present invention.

FIG. 3 is a chart showing correspondence between valve opening / closing behavior of a steam control valve and a turbine bypass valve according to the present invention, and a drop and recovery of steam pressure of steam generated from an exhaust heat recovery boiler.

FIG. 4 is a control system diagram schematically showing a control device of a conventional combined cycle power plant.

FIG. 5 is a control block diagram schematically showing the control device shown in FIG. 4;

FIG. 6 is a chart diagram showing the valve opening / closing behavior of a conventional steam control valve and a turbine bypass valve, and the drop and recovery of steam pressure of steam generated from an exhaust heat recovery boiler.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combined cycle power plant 2 Rotary shaft 3 Gas turbine plant 4 Steam turbine plant 5 Exhaust heat recovery boiler 6 Air compressor 7 Combustor 8 Fuel valve 9 Gas turbine 10 Steam turbine 11 Generator 12 Pressure sensor 13 Steam control valve 14 Condensate Device 15 Turbine bypass valve 16 Turbine bypass valve 17 Valve list detector 18 Control device 19 Turbine bypass valve setting device 20 Turbine bypass valve controller 21 Valve switching drive unit 22 Loading control unit 23 Pressure control unit 24 First comparator 25 First 2 comparator 26 memory 27 AND gate 28 switcher 29 setting device 30 switch 31 integrator 32 control device 33 turbine bypass control unit 34 valve switching drive unit 35 loading control unit 36 pressure control unit 37 turbine bypass Valve setting device 38 Controller for turbine bypass valve 39 Adder / subtractor 40 Comparator 41 Pressure sensor 42 Turbine bypass valve 43 Valve lift detector 44 First comparator 45 Second comparator 46 Memory 47 AND gate 48 Setting device 49 First switch Reference Signs List 50 second switch 51 integrator 52 switching device 53 steam control valve 54 differentiator 55 comparator

Claims (5)

[Claims] 1. A gas turbine plant, a steam turbine plant, and an exhaust heat recovery boiler are combined, and during the start-up operation of the exhaust heat recovery boiler, while the steam generated from the exhaust heat recovery boiler flows into the turbine bypass system, the steam pressure is reduced. When a certain value is exceeded, a valve closing signal is provided to the turbine bypass valve, and in a control device of a combined cycle power plant including a control unit that provides a valve closing signal to the steam control valve,
The control unit includes a loading control unit including a first switch and a second switch that perform opening and closing control of the steam control valve, and a valve that turns on the first switch of the loading control unit when the turbine bypass valve closes. A switching drive unit, a deviation calculating unit that calculates a deviation by comparing an actual steam pressure of steam generated from the exhaust heat recovery boiler with a set steam pressure while the turbine bypass valve is closed, and an output of the deviation calculating unit. Is lower than the first deviation set pressure value, the second switch of the loading control unit is turned on. When the output of the deviation calculation unit is higher than the second deviation set pressure value, the second switch of the loading control unit is turned on. A turbine bypass control unit incorporating a calculation unit for turning off the
When the steam control valve is opened when both the first switch and the second switch of the loading control unit are turned on, the calculation signal from the calculation unit of the turbine bypass control unit is cut, and the second switch is turned off. A control device for a combined cycle power plant, further comprising a switch for holding a valve opening of the steam control valve. 2. The control device for a combined cycle power plant according to claim 1, wherein a deviation calculator is incorporated in the turbine bypass controller, and the deviation calculator is an adder / subtractor. 3. The apparatus according to claim 2, wherein the adder / subtractor compares the actual steam pressure signal from the pressure sensor with a predetermined pressure signal from a turbine bypass valve closing setting device to calculate a deviation. For combined cycle power plants. 4. A turbine bypass control unit includes an arithmetic unit, which is a comparator having a set value different from the first deviation set pressure value and the second deviation set pressure value. The control device for a combined cycle power plant according to claim 1, wherein: 5. A turbine bypass control unit, comprising: a differentiator for calculating a change rate of an actual steam pressure of steam generated from an exhaust heat recovery boiler; and when a calculation signal of the differentiator is lower than a first deviation set pressure value. Turn on the second switch of the loading controller
2. The combination according to claim 1, further comprising: a comparator that cuts off when an operation signal of the differentiator is higher than a second deviation set pressure value and turns off a second switch of the loading control unit. Control device for cycle power plant.